As a device allowing an observer to visually recognize a video by incorporating an image display device which forms an image, various devices regarding a transmission type display device, for example, a head mount display (in the following, also referred to as an HMD) to be mounted on a head of the observer or the projector are proposed. Specifically, as a display applicable to the HMD or the projector, a display in which a plurality of half mirrors are disposed to enlarge a light flux for display is known (see PTL 1) and, for example, a technique in which an image for the right eye and an image for the left eye are allowed to be recognized visually and respectively when displaying the image so as to allow a stereoscopic image to be visually recognized is known (see PTL 1).
As the projector, a technique for projecting an image onto a surface (that is, three-dimensional surface) having recessed and protruded surface other than a plane is known (for example, see PTLs 2 and 3).
However, in a technique disclosed in PTL 2 or the like, even if projection to a curved surface of which the shape is decided in advance to a certain extent and which has a smooth curvature is possible, it was difficult to perform focusing on, for example, a concave surface or a convex surface having a complicated shape in which an abrupt step difference occurs.
As another problem to be solved, although there is a technique in which in a case where an image from an image display device is optically guided so as to allow a video to be visually recognized as in, for example, the HMD, the image is viewed in binocular vision by a configuration of a pair of right and left and images (image obtained by slightly shifting a common image in the right and left) different in the right and left are reflected when being viewed in binocular vision so as to perform stereoscopic vision by utilizing parallax, a distance between videos is not changed, and thus, focus adjustment (in the following, accommodation) of the eyes is constant and vergence-accommodation conflict occurs. It is desirable that natural stereoscopic vision becomes possible by eliminating the vergence-accommodation conflict as much as possible.
Furthermore, in the projector enlarging and projecting the image from the image display device, for example, in a case where a shape of a screen is not a plane, it is desirable to perform focusing especially, even in a case of a complicated concave surface or convex surface.